Extrusion of ferrous metals through dies of metal silicides



F. J. PENOZA Sept. 28, 1965 EXTRUSION OF FERROUS METALS THROUGH DIES 0F METAL SILICIDES Filed Jan. 1'7, 1963 2 Sheets-Sheet l FIG! H62 INVENTOR FRANK J. PENOZA WM M ATTORNEY Sept. 28, 1965 F. J. PENOZA 3,208,253

EXTRUSION OF FERROUS METALS THROUGH DIES 0F METAL SILICIDES Filed Jan. 17, 1965 2 Sheets-Sheet 2 Fl G. 4

FIG. 40

INVENTOR FRANK J. PENOZA ATTORNEY United States Patent 3,208,262 EXTRUSION 0F FERROUS METALS THROUGH DIES 0F METAL SILICIDES Frank J. Penoza, Wilmington, DeL, assignor to E. I. du

Pont de Nemours and Company, Wilmington, DeL, a

corporation of Delaware Filed Jan. 17, 1963, Ser. No. 252,223 Claims. (Cl. 72-364) The present application is a continuation-in-part of Application Serial No. 78,102, filed December 23, 1960, now US. Patent 3,110,092, issued November 12, 1963; U.S. application, Serial No. 78,165, filed December 23, 1960; and application, Serial No. 78,088, filed December 23,1960, now U.S. Patent 3,110,091, issued November 12, 1963.

The present invention is concerned with an improved process for extrusion of ferrous metals. More particularly, this invention is concerned with a process for extrusion of ferrous metals employing dies comprising certain silicide compositions.

Although extrusion processes have long been used for fabrication of such metals as copper, brass, and aluminum, extrusion of ferrous alloys has not been practiced as extensively for a number of reasons. Among these are the high temperatures required to achieve satisfactory billet plasticity, temperatures at which conventional dies even of heat-resistant steel lose strength and undergo rapid destruction by abrasion and deformation, and the necessity for lubrication of the die to avoid galling of the extruded metal. Glass has been found to be superior to lubricants composed of grease or oil with additives such as graphite and salt and to other types of lubricants, because of its ability to provide continuous lubrication, particularly of long extruded articles, However, use of glass lubricant with conventional dies introduced new problems; even with such lubricant, die deformation, die wear, and uneven distribution of the glass often result in so much variation in the cross-sectional dimensions of the extruded metal as to restrict its scope of use.

There are, generally speaking, three surfaces or interfaces, the frictional properties and necessity for lubrica- .tion of which must be considered. These are (1) the front face of the billet, i.e., the surface in contact with the surface of the die; this is the most critical of the three surfaces; (2) the outside surface of the billet which is in contact with the container wall; and (3) in the case of tube and other hollow extrusions, the inside surface of the billet which is in contact with the mandrel. In the extrusion of ferrous alloys, grease-type or other lubricants may be used for all the foregoing surfaces, if desired, but a glass lubricant is usually preferred, especially where a thick layer of glass is employed between the die and the billet, thereby providing a supply of glass and additional thermal insulation between the die and the billet during extrusion.

The glass used in extrusion is an item of cost and necessitates special precautions to insure the complete protection of all sliding surfaces on the press from the abrasive particles which may be deposited, and the thin film of glass which remains on the extrusions must be removed, for example, by pickling in molten caustic soda or in a mixture of sulfuric and hydrofluoric acid. The glass adhering to the container must be removed, e.g., by an ejecting disk which is passed through the container, or by rotating Wire brushes, while the die is cleaned with the aid of pneumatically powered hand tools and shot blasting. Continuity and uniformity of lubrication is essential for the production of well-formed extruded metal and to maintain this continuity a viscous lubricant is required. For this reason, the viscosity of the glass at extrusion temperature is important and different glasses are required for extrusion of different types of ferrous alloys. Moreover, use of glass lubricant requires a higher surface finish of the billet than is required with grease-type lubricant to obtain satisfactory finish on the extruded product.

Using these prior-known methods of lubricated extrusion without resort to special finishing treatments, extruded sections of ferrous alloys are generally produced in lengths of approximately 30 feet at speeds of about 1200 ft./rnin. at the die exit. When extrusions longer than 55 to 60 ft. are produced, die difiiculties become apparent. Tolerances are usually kept to -0.000+0|.030 inches for cross-sectional dimensions under 1 in. Typical total tolerance spreads for various size ranges of a cross section are:

Cross-sectional dimension, inches: Total tolerance, inches Under 1 0.031 1-3 0.062 34 0.093 Over 4 0.125

However, even though the dimensional variation of the cross section of the extrusion may be acceptable, machining or grinding operations are often necessary for attainment of a satisfactory finish, particularly with highly alloyed steels. Maintenance of such tolerances requires frequent reworking of the die and after 8-100 extrusions, depending on material and shape being extruded, the die is normally discarded.

Steel extrusions having good surface and small dimensional variation can be made in lengths of a few inches using unlubricated conventional dies. In practice, however, a graphite-in-oil die lubricant is generally used even to make such short extrusions as the poppet valves (integral head and stem) for automobile engines. If a long article is extruded without any die lubricant, the extrusion surface ,is severely galled and the die is beyond the possibility of re-use.

It is therefore the object of the preesnt invention to provide an improved method for the extrusion of ferrous alloys in which a gain in the length of extruded metal of given surface properties and dimensional variation is obtained.

It is a further object of the invention to provide an improved method for the extrusion of ferrous alloys through unlubricated dies in which outstanding surface characteristics of the extruded metal are obtained, due to a markedly lower tendency toward galling of the billet metal as it passes in contact with and through the die.

It is a still further object of the invention to provide an improved method for the extrusion of ferrous alloys in which outstanding dimensional control of the extruded metal is obtained.

The above, and other objects, which will become clear from the following description are accomplished by a hot metal extrusion process comprising the steps of heating a ferrous alloy billet to a temperature conferring plasticity and forcing the plastic billet through the orifice of a die nib composed of a defined class of refractory metal silicides. As an essential feature of the invention, the silicide nib combines in a highly surprising degree, a

number of properties which provides an improved extrusion process for ferrous alloys leading to the production of high quality extruded products, including outstanding inherent lubricity, high compressive strength and high modulus of elasticity at extrusion temperature, and generally good chemical inertness.

Silicide compositions which are suitable for use in fabricating the die nibs for use in the practice of the invention are metal silicides containing from 14-57% by weight silicon, from 11 -65% by weight a metal selected from the group consisting of Group IV-B, V-B, VI-B, VII-B, and VIII of the Period Table and at least one additional'element in an individual amount of from 1-65% by weight selected from the group consisting of Group IV-B, V-B, VI-B, VII-B, and VIII of the Periodic Table, nitrogen, boron, and carbon. The Periodic Table referred to in the foregoing definition appears in Demings General Chemistry, John Wiley & Sons, Inc., 5th Ed., chapter II. Of such silicide compositions, those having melting points above about 2100" C. are operable at higher extrusion temperatures than lower melting silicides and are generally preferred.

Included as silicide compositions suitable for the invention are the molybdenum-iron and iron-titanium silicides described in US. Patents 2,866,259 issued December 30, 1958, and 2,878,113 issued March 17, 1959, assigned to my assignee. Also included are silicides containing 8-65% by weight Mo, 2-30% by Weight Nb, 15-45% by weight Si, 1 0-65 by weight Ti, and 0-10% of an alkali or alkaline earth metal, which are described in copending US. application Serial No. 160,645, filed December 19, 1961. The alkali or alkaline-earth metal is usually introduced as an aqueous solution of metal hydroxide, carbonate, or bicarbonate. Further useful silicide compositions for fabrication of die nibs are those containing 14-65% by weight Mo, l-1'2% by weight N, 14-45% by weight Si, and 15- 59% by weight Ti, described in US. Patent 3,110,589, issued November 12, 1963. Further useful silicide compositions which may be employed are those containing 4-5- 65% by weight Mo, 1-10% by weight N, 19-53% by weight Si, and 0-10% by weight of an alkali or alkaline earth metal, described in U.S. Patent 3,110,590, issued November 12, 1963. The alkali or alkaline-earth metal is usually introduced as an aqueous solution of metal hydroxide, carbonate, or bicarbonate.

Silicide compositions most preferred for the invention contain in addition to the metal silicide per se a refractory metal oxide component, particularly an oxide selected from the group consisting of ZIO2, ZnO, and Cr O The presence of the refractory metal oxide in amounts of from 520% by weight is found to facilitate fabrication of the die nib from the silicide and is found to further improve the inherent lubricity of the formed die nib. Silicide compositions of this latter type highly suitable for the invention include those containing 14-57% by weight Si, 14- 65% by weight individually of at least two metals from the group consisting of Fe, Groups IV-B, V-B, and VI-B of the Period Table, and from about 5-20% by weight of a metal oxide taken from the group consisting of ZrO ZnO, and Cr O which are described in US. Patent 3,110,- 092, issued November 12, 1963. It is preferred that for the purposes of the present invention that the latter compositions in addition to the general composition contain 1-12% by weight of chemically combined nitrogen. Other silicide compositions containing refractory metal oxides highly useful for the practice of the present invention include those containing 20-53% by weight Si, 40-65% by weight Mo, 1-19% by weight N, and 5-20% by weight of either ZrO ZnO, or Cr O which are disclosed in US. Patent 3,110,091, issued November 1 2, 1963.

Although lubricants, i.e., glass-like or grease-type materials, can be employed, especially where long extruded articles are desired, in the extrusion process of this invention, the properties of the defined silicide die nibs are such that niblubricants are often unnecessary.

Use of lubricant is often rendered superfluous by the inherent lubricity of the nibs which promotes smooth and uniform flow of metal through the die orifice while an ancillary feature of the silicide nibs, i.e., resistance of silicides to high temperature, makes unnecessary the use of lubricant as thermal insulation of the nib during extrusion. As stated above, lubricity of the nibs is enhanced by incorporation of oxides during fabrication or by superficial oxidation of the silicide brought about for example by heating in air. The high surface finish and maintenance of exceptional dimensional tolerance of extruded shapes produced with silicide die nibs are the direct result of the ability of the nibs to resist wear and deformation and to function in the absence of added lubricant. Where no lubricant is employed, there is no necessity for cleaning the extruded metal to remove the adherent layer of lubricant which is present when glass lubricants are employed.

:Frictional conditions between die and billet influence both pressure requirements and mode of flow of metal during extrusion. Under given extrusion conditions, the lower the coefficient of friction between billet and die material, the lower the pressure required for extrusion. These benefits may be taken advantage of directly by employing a lower extrusion pressure at a given temperature or indirectly by operating at a lower temperature with attendant reduced likelihood of damaging the metal by overheating.

Owing to the unique combination of properties possessed by the above-described class of silicide compositions, particularly due to the high compressive strength and high modulus of elasticity at extrusion temperatures and high inherent lubricity, die nibs of such compositions can be employed in a wide variety of forms including laterally supported and unsupported nibs and shielded nibs. A useful form of silicide nib for the present invention is that in which radially compressive support at extrusion temperature against the disruptive forces engendered by extrusion is provided by a tightly fitting hand, ring, or casing of elastic metal. Such nib construction is described in greater detail in copending application Serial No. 78,165, filed December 23, 1960. Support bands, rings, or casings are not a necessary feature of the nibs used in the present invention, however, and can be omitted with resultant simplification in die fabrication by suitable design of the nib. A form of unsupported die nib is described hereinafter. Such nibs are generally conical or truncated conical in overall appearance with the extrusion aperture more or less centrally located.

A further type of die nib particularly useful in the present invention is the hooded or shielded nib. This type of nib comprises in addition to radially compressive support, as described above, a shield of hard metal interposed between the silicide nib and the-billet. This shield initiates shaping of the metal being extruded and protects a major proportion of the face of the silicide nib from the thrust and heat of the billet. In this type of construction, the shield can be looked upon as a roughing die and the silicide as a finishing die.

The temperatures and pressures employed in carrying out the process of this invention are those at whichthe ferrous alloy billet has adequate plasticity for extrusion. The specific temperature and pressure employed obvious- 1y therefore will depend on the composition of the alloy, the reduction ratio, and the lubricant, if any, as well as on the pressures which can be exerted by a given extrusion press. For example, nodular cast iron can beextruded at a temperature in the range of 1830 to '2010" F. while the various varieties of stainless steel, which commonly contain in addition to iron and carbon substantial amounts of chromium and nickel, smaller quantities of manganese and sometimes silicon, molybdenum, and titanium, can usually be extruded at temperatures in the range of 2010 to 2190 F. High speed tool steels can be extruded in the temperature range of 2010 to 2370 F. 'In other words, the extrusion of ferrous alloys is cess of 180,000 lb./sq. in.

mold adapted to "torm of unsupported as-finished form of unsupported association with a steel 9" diameter, such as commercial grade benzene, cyclohexane, acetone, 'or similar li uids, for example, "in that it I tent of less than about 3%,

a 200-mesh screen, after which they were ready for use iron and alloys in which iron is present in higher content by weight than any other alloying element.

The pressure required for extrusion of a .given iron duction ratio, the die approach, and the speed of extrusion. These and other factors allecting pressure requirements are well recognized in the art. Using silicide dies for difiicult extrusions, breakthrough pressures in exhave been observed.

A better understanding of the invention will be gained from the following detailed description and the drawings, in which:

FIGURE 1a is a vertical sectional view of the compact of FIGURE 1 in the as-finished form of a die nib and in condition to be mounted in a suitable holder for metal extrusion, the flare of the discharge opening being somewhat exaggerated to show this detail,

FIGURE 2 is a vertical sectional view of a graphite die the manufacture of compacts of the design shown in FIGURE =1,

FIGURE 3 is a fragmentary view in transverse section through the extrusion throat I f a special design of die nib adapted to form fluted rods by hot extrusion.

FIGURE 4 is a vertical sectional view of the as-finished die nib mounted in association with a steel back-up plate for hot metal extrusion,

a vertical sectional view of a further die nib mounted in back-up plate for hot metal extrusion, and

FIGURE 5 is a vertical sectional view of an as-finished form of die nib in condition to be mounted in a suitable holder for hot metal extrusion.

PREPARATION OF S'ILICIDE COMPOSITIONS The general procedure utilized in preparing the compositions for fabrication of the dies used in the Examples following The desired components in the form of airwere weighed out and placed together in a l-gal'lon ball mill jar. A liquid additive description. dry powders zen was evaporated. At this point, a small amount of NaOH aqueous solution was added to the powders. e mixed powders were then dried to a moisture concrushed and passed through in nib fabrication.

As a typical example, in preparing a powder having the nominal composition Fe60Mo20Si with 10% added, 1080 g. of Mo powder, 720 g. of ferrosilic on (nominally 50% Fe, 5 0% Si) and 200 g. of ZrO were placed in a porcelain jar along with about of the jar volume (1262 cc. random packed) of diameter flint (silica) pebbles, plus 1000 cc. of benzene. The nominal dry percentage composition of this mixture was thus The jar was sealed and rodrilled centrally to receive a rate of extrudate througput,

. The throat in the nib as .length about 0.010"

tated at 67 r.p.m. tor 72 hours on a ball mill frame. After milling, the contents of the jar were discharged onto a porcelain tray, the benzene evaporated and the tfiint pebbles separated from the powder by coarse screening. Following this, 1050 cc. of 4.76% aqueous NaOH solution was stirred into the powder, which was then oven-dried for 2 hours at C., crushed with a mortar and pestle, and screened through a 200-mesh screen, after which the powder was stored in closed containers until nibs were to be made up therefrom.

PREPARATION OF DIE NIB Turning now to the die nib manufacture per se, extrusion dies employed in Examples 1-8 were provided with nibs which had the as-pressed shape of FIGURE 1 and were thereafter finished to the final shape of FIGURE 1a, after which they were mounted in suitable support housings and were then ready for use in metal extrusion.

vention, and that some shapes as regards specific alloys to perform better than others be extruded, reduction ratios, extrusion temperatures, whether or not lubricants are used during the extrusion and many other considerations. The nib shape shown was settled upon to permit evaluation of test results without complication introduced as a result of variations in nib profiles, and proved to be highly effective.

In most cases, the nibs employed in Examples 1-8 below measured, in the finished form shown in FIGURE 1a, 1%" diameter x l long. The inlet of the nib was provided with a frusto-conical mouth sloped at an angle of about 45 and of a depth b, which measured 0.40". length h of the straight cylindrical throat c was from to A" in all cases and the surfaces of both the inlet ground and polished to a high finish.

.2-5", the degree of rather noncritical.

FIGURE 1 is actually that formed by two concentric frusto-conical surfaces, the outer one of which is inclined to the horizontal at an angle a=15, whereas the inner one is inclined to the vertical at an angle 2:45". two surfaces intersect in a toroidal surface which is formed to a radius of 0.02", the lower extremity of which surface is located on the level of line xx, a distance d= inwardly from the outside circumference of the nib body as pressed. The specific profile of hell mouth described appears to be particularly advantageous from the standpoint of ready disengagement of the compaction mold piston. As indicated in FIGURES 1 and la, the top of the nib is ground off on line x-x as a finishing operation to obtain the nib form of FIGURE 1a. pressed is a straight cylindrical undersize diametrically to provide for the grinding and polishing to the final condition of FIGURE 1a.

The nibs were formed by molding within mold which, as shown in FIGURE 2, comprises a cylindrical body 10 about 5 /2" in height provided centrally with a bore 9 of the same size as the unfinished outside end with a close-fitting annular Finally, a 78" thermocouple well 18 is preferably provided in body 10.

In nib manufacture, it will be understood that a complete weighed and mixed powder charge is first placed within bore 9, closed at the bottom by base plate 11 and provided with core piece 12, if the die throat is to be pre formed. The charge is then tamped manually with the aid of plunger 17 until enough powder has been introduced into the mold to produce a nib of the length desired. At this point the entire mold and its charge is placed upright within a hydraulic press and pressure applied to plunger 17 while base plate 11 is supported in place by the press platen and the entire die mold is heated, preferably by electric induction heating, until the alloying and sintering hereinbefore described is completed. It is preferred to shield the die mold with two or more thicknesses of asbestos paper wrapped circumferentially around the outside of body 10, and also on the top and bottom surfaces of the die mold, to preserve uniform temperature conditions within the die mold and, at the same time, protect the mold from oxidation by the air.

A preferred procedure is to apply downward pressure on plunger 17 in increasing increments. Thus, with the die mold cold, 1000 p.s.i. is applied at room temperature, and this pressure maintained quite steadily until the die mold reaches 1000 C., as indicated by a thermocouple mounted in well 18. At this point the pressure is increased to 2000 p.s.i. and this is continued substantially unchanged until the die mold temperature reaches 1300 0, when the pressure is increased to its highest level, e.g., 3000 p.s.i. and held at the latter value for about 15 minutes. The alloying-sintering has now been completed and good homogeneity has been obtained by this time, so that heating can be discontinued and the graphite die mold removed from the induction heating apparatus.

Core pin 12 is then removed from the hot mold by forcing it out with an arbor press, after which the hot mold, still containing the nib within its cavity, is placed within a metal container which is loaded with alumina spheres. The mold is covered with the spheres, which the mold from oxidation, and allowed to cool to room temperature, after which the mold is placed in an arbor press and plunger 17 pushed downwardly without support applied to the underside of base plate 11. This forces plate 11 and sintered nib 16 out of the bottom of the graphite mold, after which the mold can be reloaded to make another nib. It will be understood that the mold and its appurtenances can be used over and over again indefinitely.

The surface areas of the nib are belt-sanded and, thereafter, ground to parallel surfaces at top and bottom, as

well as to desired height, using a silicon carbide or diamond grinding wheel. The frusto-conical inlet and the nib throat are then finished, both as regards surface quality and dimensions. Finally, the nibs employed in Examples 1-8 were formed circumferentially to fit within an elastic metal support housing as described in copending US. Application Serial No. 78,165, hereinbefore mentioned, after which the complete die is ready for hot metal extrusion service.

Extrusion die nib compositions for Examples 1-8 are tabulated in Table I. These were made up from the ingredient system denoted, to which was added of one of the metal oxides: ZnO for No. VI, ZrO for Nos. I, II, III, IV, V, and VIII, and Cr O for No. VII. The ingredients were thoroughly mixed by ball-milling operation and converted to nibs under the conditions indicated. Typical times employed to raise to sintering temperature are given for some of the nibs as well as densities of product and Rockwell A hardness (usually in duplicate). In all instances the nib orifice was shaped by the use of a graphite core during the hot pressing-sintering operation, except in the case of Nos. III and V, where the hole was drilled by electro-spark machining.

TABLE I Nib Ingredient system Soak time Composition expressed in minutes at Density RockwellA No. nominal percent sintering g. lcrnfi hardness temp. 20 6.36 88, 20 6 33 85, 86 25 6.43 86, 87 25 (i. 79 88, 89 20 6. 58 85, 86 5 6. 22 85, 86 5 5.98 87 5 85, 86

a Siutering conditions were 1300 O. and 3000 IbJsq. in. pressure. b 20% ZrO was added; the finished nib was 1% outside diameter.

0 Approximate throat diameter of nib d Approximate throat diameter of nib c VI and VII: 90 minutes taken to heat each to sintering temperature using a 20 kw. induction furnace.

f VIII: 55 minutes taken to heat to sintering temperature using a 50 kw. induction furnace.

The preparation of dies used in Examples 9l2 hereinafter was similar in all respects to the procedure described in the foregoing. The shape of the final dies was as illustrated in FIGURES 4 and 4a; achieved by pressing to approximate shape using a graphite core for formation of the nib orifice 19, followed by finishing to final dimensions. The material employed was a ZrO -modified Mo- N-Si composition containing 53% M0, 6.5% Si, and 10% ZrO on a weight basis. The nib 20 in each case was supported during extrusion by steel plate 21 having a recess for receiving the nib providing a clearance between the CD. of the nib and the I.D. of the recess in the steel plate of approximately 0.002. Nib 20 in Figure 4 projected A above steel plate 21 and nib 20 in FIGURE 4a projected /2 above the top of support plate 21.

It is preferred to mold-form the nib throats, at least to rough prefinished state, in the course of manufacture of the nibs themselves, because in this way complex extrusion passages can be formed by simply machining the mating reverse configuration on the outside of the easily machinable graphite core pin 12. One such intricate transverse throat profile is that shown in FIGURE 3, which was adapted to produce fluted extruded rods. However, if desired, the nib extrusion passages can be formed by electro-spark machining, diamond boring, or ultrasonic machining.

Each nib was subjected to a searching visual inspection for cracks or other flaws before being passed to extrusion testing, so that any cracking occurring as a result of mounting in the support housings, finishing or in the extrusion itself could be identified.

HOT METAL EXTRUSION The process of the invention is illustrated by the following examples which demonstrate the inherent lubricity, high-temperature hardness, and other excellent properties of silicide nibs. In some of the examples no lubricant whatever was employed, whereas, in others, a suspension of very fine graphite in a light hydrocarbon was used as a means of reducing the friction of feeding the billet through the steel directing sleeve, or container, upstream from the die itself. In view of the limited amount of graphite-in-oil used, as well as the temperatures existing during the extrusion tests (at which the oil carrier flashes off), little or no lubricating effect persisted into, or during, the extrusion per se. This is confirmed by the fact that the extruded products were obtained with satisfactory finishes which required no post-extrusion cleansing, as compared with the visibly contaminated products of the prior art. Accordingly, such extrusions can be considered substantially free of lubricant, even where a lubricant is applied as a preliminary to billet feed through the container.

The respective nib and billet temperatures reported in the examples are those which existed at the commencement of extrusion work. The tendency is for apparatus resulted in an irregular pressing and process material to all reach a common temperature during extended operation. In addition, there is, of course, a large amount of heat generated by the extrusion work itself, so that temperature conditions existing at any given time during the extrusion process are dependent on previous events.

The term reduction ratio is defined as the ratio of the cross-sectional areas of billet fed to extrudate product. The term nib washout refers to progressive enlargement of the nib mouth occurring as a consequence of extrusion.

Example 1 Nib composition No. III, Table I, was utilized to extrude A.I.S.I. 1018 steel with the nib temperature 850 F. and the billet temperature 2100 F. The reduction ratio was approximately 20:1, the billets fed being 2" long x 0.950" diameter.

Two series of extrusions were made, the first consisting of seven 0.223" diameter extrusions in lengths of 30"-40" each using a glass lubricant which was sprinkled onto the feed stock as a powder :20 mesh size. This pressure which caused the nib to crack circumferentially at the inlet end because of the stock sticking. The crack was upstream from the working area of the nib and out of contact with the billet, so that there was no effect on the extrusion.

The second series of tests dispensed with lubricant altogether, and six more extrusions of the same dimensional data as the first series were made on the same die. This resulted in smooth operation without any additional cracking of the nib and with excellent surface finish on the extrudate and no nib washout.

Example 2 Nib No. IV, Table I, was utilized no extrude A.I.S.I. 1018 steel with the nib temperature 850 F. and the billet temperature 2100 F. The reduction ratio was approximately 2021, the billets fed being 2" long x 0.950 diameter. The extrudate lengths were 30-40" and 23 separate extrusions were made with the die using a very light application of graphite-in-oil to the container upstream from the die.

The extrudate had a good surface finish and checked diametrically in the range 0.221"-0.2215". Slight hairline cracks developed on the die nib during this test but none of the cracks were so serious as to have a detectable surface etfect on the extrudate. No nib washout was noted.

Example 3 i die. All extrudate rods checked diametrically at 0.218"

0.220 and had good surface finish. No additional cracks appeared in the nib, nor was any washout noted.

Example 4 Nib No. VIII, Table I, was utilized to extrude A.I.S.I. 416 stainless steel with the nib temperature 850 F. and the billet temperature 2300 F. The reduction ratio was approximately 1, the billets fed being 2" long x 0.950

1 diameter. The extrudate lengths were "-40, and three extrusions were made using light graphite-in-oil application to the container.

No cracks developed on the die nib and the extruded 10 product had a good surface finish. There was 110 die washout.

Example 5 A nib of composition No. I, Table I, was made up with an extrusion throat of cross-section shown in FIGURE 3, i.e., with four fins disposed 90 apart around a circular central body. The nib was utilized to extrude two types of ferrous metal in sequence. The reduction ratio in all extrusions was the same at 3:1 and the billets fed were 2" long x 0.950" diameter.

The extrusions were as follows, a light graphite-in-oil lubricant being used on the container in all instances.

(a) Stock fed: A.I.S.I. 1018 steel. The nib temperature was 850 F., the billet temperature 2100 F. Two extrusions were performed without any cracks develop ing in the nib and with good surface finish on the extrudate.

(b) Stock fed: H-13 tool steel. The nib temperature was 850 F., the billet temperature 2400 F. Two extrusions were performed, with good surface finish obtained on the product and no cracks developing in the nib.

Example 6 Example 7 The nib of this example had composition No. VI, Table I, i.e., 20Fe60Mo20Si plus 10% ZnO, and measured 1% outside diameter x 1 long with a 0.610" diameter throat. The nib was preheated to 850 F., at which time A.I.S.I. 1018 steel was extruded therethrough, the billet size being 1%" diameter x 2%" long, and the billet temperature 2100 F. The reduction ratio was approximately 5:1.

Only one extrusion, without lubricant, was made through the die nib, because of operating difliculties with the press; however, the product, measuring 9" in length, had a good surface finish, and the nib did not show any cracks.

Example 8 The nib of this example had composition No. VII, Table I, i.e., 20Fe60Mo20Si plus 10% Cr' O and measured 1% outside diameter x 1" long with a 0.610" diameter throat. The nib was employed for hot. extrusion of A.I.S.I. 1018 steel. The billet feed temperature was 2100 F., billet size 1%" diameter x 2 /8" long, and the extrusion ratio was 5: 1. One extrusion 9" long was made through the nib, good surface finish being obtained without cracking of the nib.

Examples 9-12 Billets of 1095 steel and of stainless steel 2" in diameter by 3" long were extruded at a reduction ratio of 18:1 to produce /2" round rods. Details are shown in Table II. The container and die were preheated to 750 F. and were cleaned between extrusions; billet temperature is indicated in the table. A vertical hydraulic press was employed capable of exerting a maximum force of 360 tons.

In each case the extruded rods had good dimensional tolerance and satisfactory surface quality.

TABLE II Extruded Rod Nib Billet Diameter (inches) Ex. Type Ferrous Alloy Nib Lubricant 1 Temp, No. Fig. 1 F.

Nose Butt 4 2, 100 0. 495 0.502 4 1, 900 0.502 0.502 4a 2, 150 0. 490 0. 497 4a (1 l095-Steel Glass pad 1, 900 0. 499 0.505 (2) 204 Stainless Steel do 2, 150 0.495 0. 498 (3) 304 Stainless Steel do 2, 150

1 All nibs were produced from a composition containing 53.0

M0, 6.5 N, 305 Si, 10 Z102.

-Grapl1ite-in-oi1 on container wall and billet surface was used in all cases.

The following two examples were experimental runs devised to simulate commercial scale operation in order to illustrate the improvement available over conventional operations and indicate the outstanding commercial potentiality of the method of the invention.

Example 13 A die nib, as illustrated in FIGURE 5, composed of 43.9Mo25.3Si4.6N16.2Ti10Zr0 was employed to prepare /8" round rod from No. 304 stainless steel at a reduction ratio of 104:1. The die nib was prepared in a manner similar to that described for the preparation of nibs for Examples 1 to 8, the dimensions of the nib being: R=%"; 11:0.220"; :0.384; g=5. The die nib was fitted with a suitable support housing in the manner similar to that already described for the die nibs used for extrusion in Examples 1 to 8. The extruded lengths averaged 73 in length and were produced at speeds ranging from 1040 ft./min. up to in excess of 4000 ft./min. representing a 2-3 fold gain in production speeds over extrusions with conventional dies. Seven such lengths were produced and the die nib was still useable. A billet 4 in diameter and 8" long was employed and was preheated to 2150 F. The container was at 950 F. and the die at 900 F. prior to extrusion. Glass lubricant was employed in the form of a glass pad between billet and die and the hot billet was rolled in glass powder prior to extrusion. A breakthrough pressure of about 150,000 p.s.i. was observed. After removal of 2-3 mils thickness of glass, uniform rod having good surface characteristics was produced. The total washout during the seven extrusions was only 7 mils measured on the die diameter.

Another die nib having the composition and dimensions described above was employed for the extrusion of A286 stainless steel. The billets were heated to 2000 F. and reduction ratio was 104:1. Glass lubricant as described above was employed. Two 73 lengths of /8" rod were produced having good surface finish and uniformity of diameter.

Example 14 A die nib having the composition and dimensions described in Example 13 was employed in the extrusion of 446 stainless steel. A vertical press was employed and the inside of the billet container swabbed with graphitein-oil lubricant. To prevent lubricant from draining onto the die face, excess lubricant was removed by passing a dummy through the container before the die was inserted under the container. Three billets 2" in diameter and 4" long, heated to 2270 F. were extruded with container and die preheated to 750 F. Reduction ratio was 31:1 and breakthrough pressure 90,000 p.s.i. The product was /8" rod in about 8' lengths having good surface finish. Washout in the nib was negligible as indicated by comparison of rod diameter at the nose (0.373") and butt (0.374") of the extrusion.

In a similar manner 3 billets of 446 stainless steel were extruded using a nib having the above dimensions composed of 17Fe51Mo17Si15ZrO Again the rod proconferring plasticity to said billet and forcing said billet through the orifice of a die nib comprising a metal silicide composition consisting essentially of from 14-57% by weight Si, from 1060% by weight of a metal elected from the group consisting of Group IV-B, VB, VI-B, VIIB, and VIII of the Periodic Table, and at least one additional element in an individual amount of from 165% by weight selected from the group consisting of Group IVB, V-B, VI-B, VII-B, and VIII of the Periodic Table, nitrogen, boron, and carbon.

2. A method for the hot extrusion of ferrous alloys comprising heating a ferrous alloy billet to a temperature conferring plasticity to said billet and forcing said billet through the orifice of a die nib comprising a metal silicide composition consisting essentially of from 14-57% by weight Si, from 1065% by weight a metal selected from the group consisting of Group IVB, V-B, VI-B, VII-B, and VIII of the Periodic Table, up to 10% by Weight a metal selected from the group consisting of alkali and alkaline-earth metals, and at least one additional element in an individual amount of from 165% by weight selected from the group consisting of Group IV-B, V-B, VI-B, VII-B, and VIII of the Periodic Table, nitrogen, boron, and carbon.

3. A method for the hot extrusion of ferrous alloys comprising forcing a ferrous alloy billet at a temperature in a range of 16502450 F. through the orifice of a die nib fabricated from a metal silicide composition consisting essentially of from 1457% by weight Si, from 1065% by weight of a metal selected from the group IV-V, V-B, VI-B, VIIB, and VIII of the Periodic Table, and at least one additional element in an individual amount of from 165% by weight selected from the group consisting of Group IV-V, V-B, VI-B, VII-B, and VIII of the Periodic Table, nitrogen, boron, and carbon.

4. A method for the hot extrusion of ferrous alloys comprising forcing a ferrous alloy billet at a temperature in a range of 16502450 F. through the orifice of a die nib fabricated from a metal silicide composition consisting essentially of from 1457% by Weight Si, from 10-65% by weight of a metal selected from the group consisting of Group IV-B, V-B, VI-B, VII-B, and VIII of the Periodic Table, from 165% by weight individually of at east one additional element selected from the group consisting of Group IV-B, V-B, VI-B, VII-B, and VIII of the Periodic Table, nitrogen, boron and carbon, and from 520% of a metal oxide taken from the group consisting of ZrO ZnO, Cr O 5. A method for the hot extrusion of ferrous alloys 1s Comprising forcing a ferrous alloy billet at a temperature in a range of 1650-2450 F. through the orifice of a die nib fabricated from a metal silicide composition consisting essentially of from 14-57% by weight Si, from 14-65% by weight individually of each of the metals Fe and Mo, and from 5-20% by weight ZrO 6. A method for the hot extrusion of ferrous alloys comprising forcing a ferrous alloy billet at a temperature in a range of 1650-2450 F. through the orifice of a die nib fabricated from a metal silicide composition consisting essentially of from 15-45% by weight Si, -65% by weight Ti, 8-65% by weight Mo, 230% by weight Nb, and from 5-2 0% by weight ZrO 7. A method for the hot extrusion of ferrous alloys comprising forcing a ferrous alloy billet at a temperature in a range of 16502450 F. through the orifice of a die nib fabricated from a metal silicide composition consisting essentially of from 14-57% by weight Si, from 14-65% by weight individually of each of the metals Fe and Ti, and from 5-20% by weight ZrO;;.

8. A method for the hot extrusion of ferrous alloys comprising forcing a ferrous alloy billet at a temperature in a range of 1650-2450 F. through the orifice of a die nib fabricated from a metal silicide composition consisting essentially of from 20-53% by weight Si, from 40-65% by weight Mo, from 1-19% by weight N, and 5-20% by weight ZrO 9. A method for the hot extrusion of ferrous alloys comprising forcing a ferrous alloy billet at a temperature in a range of 1650-2450 F. through the orifice of a die nib fabricated from a metal silicide composition consisting essentially of from 14-45% by weight Si, from 14-65 by weight Mo, from 15-59% by weight Ti, from 1-12% by weight N, and from 5-20% by weight ZrO 10. In the method of hot extrusion of ferrous alloys by heating a ferrous alloy billet to a temperature conferring plasticity to said billet and forcing said billet through the orifice of a die nib, the improvement comprising employing as a material of construction for at least said orifice of said die nib a metal silicide composition consisting essentially of from 14-57% by weight Si, from 10-65% by weight a metal selected from the group consisting of Group IV-B, V-B, VI-B, VII-B and VIII of the Periodic Table, and at least one additional element in an individual amount of from 1-65 by weight selected from the group consisting of Group IV-B, V-B, VI-B, VII-B, and VIII of the Periodic Table, nitrogen, boron, and carbon.

References Cited by the Examiner UNITED STATES PATENTS 1,430,400 9/22 Parsons et a1 207-17 2,219,442 10/40 Chesler et al. 25-156 2,866,259 12/58 Bechtold 29-1825 2,878,113 3/59 Bechtold 29-182 OTHER REFERENCES The Extrusion of Metal, 2nd Ed, Pearson and Parkins, John Wiley and Sons Inc, N.Y., 1960 (pages 238-243).

CHARLES W. LANHAM, Primary Examiner.

MICHAEL V. BRINDISI, Examiner.

UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 208 262 September 28 1965 Frank J. Penoza It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 7, line 40, after "which" insert shield column 8, line 27, for "6.5% Si, and" read 6.5% N, 30.5% Si, and column 12, line 29, for "10-60%" read 10-65% same line 29, for "elected" read selected line 55, after "group" insert consisting of Group lines 56 and 59, for "IV-V", each occurrence, read IV-B Signed and sealed this 3rd day of May 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A METHOD FOR THE HOT EXTRUSION OF FERROUS ALLOYS COMPRISING HEATING A FERROUS ALLOY BILLET TO A TEMERATURE CONFERRING PLASTICITY TO SAID BILLET AND FORCING SAID BILLET THROUGH THE ORIFICE OF A DIE NIB COMPRISING A METAL SILICIDE COMPOSITION CONSISTING ESSENTIALLY OF FROM 14-57% BY WEIGHT SI, FROM 10-60% BY WEIGHT OF A METAL ELECTED FROM THE GROUP CONSISTING OF GROUP IV-B, V-B, VI-B, VII-B, AND VIII OF THE PERIODIC TABLE, AND LEAST ONE ADDITION ELEMENT IN AN INDIVIDUAL AMOUNT OF FROM 1-65% BY WEIGHT SELECTED FROM THE GROUP CONSISTING OF GROUP IV-B, V-B, VI-B, VII-B, AND VIII OF THE PERIODIC TABLE, NITORGEN, BORON, AND CARBON. 